1. Field of the Invention
The present invention relates to a plane display element having pixel electrodes arranged like a matrix.
2. Description of the Related Art
In a plane display element comprising a plurality of switching elements such as thin film transistors (hereinafter abbreviated to TFT) provided in the proximity of an intersection of scanning line and signal line, an array substrate on which pixel electrodes are arranged like a matrix and switched by the switching element, an opposite substrate having an opposite electrode and an optical modulation layer such as liquid crystal material sealed in the gap between the array substrate and the opposite substrate, it is necessary to prevent uneven display of each pixel electrode during the manufacturing process by eliminating auxiliary capacity difference caused by deviation in alignment of pixel elements and scanning lines.
In a conventional plane display element, as shown in FIG. 6 to FIG. 8, one end portion 4a of a pixel electrode 4 rides over adjacent another scanning line 2 on an array substrate 5 which drives pixel electrodes 4 arranged like a matrix by TFT 3 put in the proximity of an intersection of signal line 1 and scanning line 2. With this structure, the area to overlap a pixel electrode 4 and a scanning line 2 is held constant regardless of whether there is alignment deviation of the pixel electrode 4 and scanning line 2 (or regardless of the degree of the deviation), and thereby the value of auxiliary capacity 50 can be held constant.
In a plane display element using such array substrate 5, to prevent image burn-in, an image is usually displayed by inverting the potential polarity of a pixel electrode to be reverse to that of the opposite electrode for each display frame. As a pattern of inverting the potential polarity of pixel electrode, it has been recommended in recent years to adopt in a plane display element a driving pattern invert the polarity of adjacent pixel electrodes along a scanning line and invert the polarity of pixel electrodes arranged along a signal line for every two pixels.
However, it has also become known that the inversion of the potential polarity for every two pixels arranged along a signal line causes uneven display appearing as a horizontal stripe in the direction along the scanning line when a half-tone raster image is displayed.
The vertical-stripe-like uneven display raises that since a parasitic capacity 51 is generated between the adjacent pixel electrodes keeping narrow space along the signal line of a plan display element, when a half-tone raster image is displayed in the driving method of inverting the potential polarity of the pixel electrodes arranged along the signal line for every two pixels, the pixel potential Vp of the previous stage is shifted by the parasitic capacity, as shown in FIG. 7.
In other words, if the potential polarity of the pixel electrodes connected to the scanning line to be scanned next is the same, the pixel potential written in the pixel electrodes connected to the scanning line of the previous stage shifts in the direction to increase the voltage impressed to a liquid crystal layer 52. Whereas, if the potential polarity of the pixel electrodes connected to the scanning line to be scanned next is different, the pixel potential written in the pixel electrodes connected to the scanning line of the previous stage shifts in the direction to decrease the voltage impressed to the liquid crystal layer 52.
As a result, the voltage from the pixel electrode to the liquid crystal material becomes different for every one scanning line, and horizontal-stripe-like uneven display occurs in the plane display element, and the display quality is debased.